In sewage treatment plants, heavy mineral matter called “grit,” forms part of the fluids that need to be processed and segregated from other fluid material. Grit is principally made up of sand and soil, but can also contain cinders, coffee grounds, seeds, corn, and other coarse sediments. As grit cannot be treated, reduced in size or eliminated by treatment methods, it needs to be physically removed. Grit presents a problem to wastewater treatment as it is hard and abrasive; it wears pumps and other mechanical devices; it is heavy and accumulates in clarifiers, treatment basins, digesters, et al, where it must often be removed by hand.
U.S. Pat. No. 4,767,532 issued in Aug. 30, 1988 to Smith & Loveless inc., discloses a grit selector having an upper settling chamber and a lower grit storage chamber. The settling chamber communicates with the grit storage chamber through an opening in a transition surface there between. An influent flume directs influent liquid directly into a lower portion of the settling chamber. An effluent flume withdraws effluent liquid from an upper portion of the settling chamber. The influent flume and effluent flume have a common centerline with the effluent flume being positioned at an elevation above the influent flume. A baffle member extends into the settling chamber for directing the influent liquid stream outwardly towards a lower portion of the periphery of the settling chamber. Influent fluid forcibly flows into the settling chamber in a tangential fashion, which induces rotational circulation inside the settling chamber. A rotating blade sustains the rotational circulation brought about initially by the incoming tangential fluid flow. Evacuation of sand and other grit material is done mainly under gravity into bottom grit pit, while water escape is performed once again under tangential flow bias.
A problem with such prior art grit removal apparatuses relates to design limitations in the orientation and size of the effluent flume liquid flow channel exiting from the apparatus settling chamber, compared to the influent flume liquid sewage flow channel. In particular, design borne flow load limitations require that:
1. the inner diameter of the effluent flume flow channel be substantially the same as the inner diameter of the influent flume flow channel; and
2. the general orientation and flow direction of the effluent flume flow channel be the same as that of the influent flume flow channel, i.e. no angular deviation (e.g. a right angle deviation) from the flow direction of the influent flume flow channel is allowed relative to the flow direction of the effluent flume flow channel, for the prior art grit removal apparatus to remain operational.